A stirring or agitating apparatus of this type is known, for example, from the German laid-open paper DE-OS No. 33 20 891. This apparatus is based on the principle of so-called "glide grinding" which enables, in particular, the surface polishing of workpieces and the comminution, granulation or agglomeration of particles to be carried out. Typical for the process of glide grinding is the continuous circulation and mixing of a filling of loose particles or workpieces under primarily shearing forces, which make themselves conspicuous in a rolling of the particles or workpieces being treated. Treating materials, such as polishing mediums or materials, may be added in particular for the glide grinding of workpieces. During the treatment of particles, their shape alters to become more spheroidal. The size of the particles is reduced during glide grinding and comminution but generally increased during granulation or agglomeration.
A number of apparatuses are available for carrying out glide grinding methods, e.g. rotary tumblers, rotary bell-shaped receptacles, rotary discs, vibrators and stirring or agitating receptacles. More detailed information on these apparatuses and methods may be found in H. E. Hinz "Gleitschleifen" (=glide grinding), Expert publishing house, Grafenau 1980 and on granulation or agglomeration in P. J. Charrington and R. Oliver "Granulation", Haeyden & Son, Rheine 1981.
Centrifugal stirring or agitating apparatuses are particularly favourable. They consist of a cylindrical vessel comprising a rotary stirring tool, usually in the form of a stirring disc on the vessel floor. The mass produced products to be treated undergo a toroidal movement in the vessel. This is characterized by the Froude number which is defined as the ratio of centrifugal acceleration to the acceleration due to gravity. It is within the range of between 10 and 100. Furthermore, the specific volume capacity is very important for these methods. The values should be as high as possible, approximately 100 kW/m.sup.3.
A disadvantage of all known centrifugal stirring apparatuses is the fact that they may be operated only in batches, have only a low specific volume capacity and are subject to high wear and tear in the case of stirring tools with convex profiles.
Operation in batches is understood to mean that the apparatus has to be filled with the loose material or mass produced products in a complicated and time-consuming manner, usually manually, before treatment can commence and emptied again once treatment is concluded. Continuous operation with, in particular, automatic feeding and discharge of the materials to be treated has not so far been possible.